Petroleum distillate and method of improving



. Patented duty 21, i4?

,a white.

PETROLEUM DHSTHLLATE AND Ii/EE@ED Eugene '1. Scafe and Elohim Herman, Woodhury,

N. 3., assigncrs to sceony 'tacnum @ii llumpany, incorporated, New York, N. 2., a cor= poration or New York No Drawing.

4. (Claims. 2

This invention has to do with the stabilization of light petroleum distillates and is more speciflcally concerned with inhibiting the deleterious effects of certain constituents in petroleum distillates of the type which are marketed as solvents and the like, by the addition thereto of novel improving agents.

As is well known to those familiar with the art, the marketability of petroleum distillate products is governed by various specifications,

depending on the contemplated use, which in many instances involves the use of tests to detect the presence of constituents having an undesirable efiect on the ultimate use of the prodnot. For example, in the case of light petroleum distillates destined for use as solvents, the so-called Blackening test (ASTM D 235-39) i employed primarily to detect the presence oi free sulphur, loosely-bound sulphur in various sulphur compounds or other constituents which might react with or discolor the constituents of lacquers, paints, varnishes, etc. This test involves immersing a polished copper strip in boiling solvent for thirty minutes, the blackening of the strip being cause for rejection. A similar test is applied to gasoline and other 138" troleum products.

It has been observed that most petroleum solvents, of ASTM boiling range 270-400 F., produce a discoloration instead of an actual blackening. This discoloration varies from a reddishcopper color to a purple cr yellow, and in cases where it is more than a slight discoloration it is cause for rejection by many consumers. It is, therefore, highly. desirable to eliminate such discoloration in petroleum distillates, particularly those which are destined for use as solvents.

The discoloration in the test above referred to is not eliminated by conventional refining procedures such as treatment with aqueous sodium hydroxide, alkaline sodium plumbite, sulphuric acid, Attapulgus clay or hydrogen.

The present invention is predicated upon the discovery that the aforesaid discoloration in the socalled Blackening test can beinhibited in light petroleum distillates such as petroleum solvents and the like, by incorporating a minor proportion of a thiophenol compound in the solvent. Contrary to accepted theories on the inhibition of such materials, we. have found that certain thiopnenol compounds when added in small amounts to light petroleum solvents will improve such solvents suflciently so as to come well within the standards set by the trade. Thus,

Application Fehruary as, rare, Serial No. asaesa Lug I we have the anomalous, and surprising, result that sulphur in a certain class of compounds or certain compounds containing sulphur will inhlbit the activity of free sulphur and looselybound sulphur in certain sulphur-containing eompounds as well as other undesirable ingredients present in light petroleum solvents.

The thiophenol compounds contemplated by the present invention are characterized by the general formula, 7?

wherein R is an aromatic radical or an alkyl substituted aromatic radical, such as alkyl substitutedor unsubstituted-phenyl, naphthyl, diphenyl, and the like. We have discovered that compounds of this general class when added in small amounts to light petroleum solvents containing the aforesaid undesirable materialsand which normally tend to cause substantial discoloration of a copper strip immersed for thirty minutes in the boiling solvent, will inhibit this discoloration. Typical compounds of the foregoing general class are thiophenol, p-thiocresol, thio=beta-naphthol, dimethyl thiodiphenyl, etc. Particularly preferred is thiophenol which is sufficiently volatile to vaporize with the solvent in which it is incorporated; thus no residue remains which may interfere with the proper functioning of other ingredients in paints, varnishes, lacquers, etc.

Broadlmthe invention contemplates the stabilization as hereinbeiore described of all light petroleum distillates, particularly those useful as solvents. Preferred for use as solvents are the highly aromatic cracked petroleum. distillates and particularly preferred are light petroleum solvents having an initial boiling point not lower than about 200 F. and end point of about 8%? F., in which the copper strip discoloration problem is acute.

To demonstrate the effectiveness of the foregoing class of sulphur compounds as improving agents for the marketability of light petroleum distillates, several such distiilates with and with= out thiophenoi were subjected to the copper strip hlaolrening'test, a description of which is given below. This test is designed primarily to detect the presence of reactive sulphur which might react with or discolor the constituents of paints, varnishes, lacquers, etc. The test method specifies that the blackening or material discoloration of a polished copper strip when immersed in the boiling solvent for thirty minutes shall be cause for rejection or the solvent. some Procedure A clean strip of mechanically polished pure sheet copper is placed in a glass tube and a sumcient quantity of the solvent to be tested is added.

to completely cover the strip. The test tube is preferably immersed in an oil bath maintained at a temperature slightly higher than the initial boiling point of the product. The sample is kept boiling without any actual distillation taking place for thirty minutes, after which the copperstrip is examined for discoloration or blackening.

Table Per Cent of Sol- Boiling vent Prior Treatment Range ThAiol llgnol I I )iscoloratron A 2 lbs. sul huric 280-354 None Purple.

acid/bb 0. 005 Reddish copper. 0.01 Very slight teddish copper. B l0 lbisdlilgphuric 280-354 None Purple.

0.005 Reddish copper. 0.01 Very slight reddish copper. C Caustic washed 310-395 None Yellow with purand clay illple.

tered.

- 0. 01 Reddish copper.

The results tabulated above illustrate that solvents, unacceptable to consumers because of the reactivity of constituents present therein, are improved substantially by the addition oi small amounts of thiophenol (a typical compound of the class contemplated by this invention) to be acceptable to the same consumers. The quantity of improving agent to be added to a light petroleum distillate, such as a petroleum solvent of the type referred to, may vary from 0.001% to 0.05% depending on the degree of discoloration normally produced by the distillate, and the maximum amount to be added depends upon the total sulphur specification. In general, however, it appears that from about 0.001% to about 0.01% of an improving agent of the typecontemplated herein is sufficient to bring light petroleum distillates well within the standards set by the trade.

It is to be understood that although we'have hereindescribed and illustrated the present invention with certain illustrative petroleum distillate blends, the invention is not restricted to the specific examples given but includes Within its scope whatever changes fairly come within the spirit of the appended claims.

Weclaim: v 1. The method of stabilizingalight petroleum solvent which, when boiling, normally causes substantial discoloration of a copper strip immersed therein for thirty minutes, which consists of admixing with said solvent a minor proportion, from about 0.001 per cent to less than 0.05 per cent, by weight, sumcient to inhibit said discoloration, of a compound characterized by the general formula: 1

wherein R is an aromatic radical selected from 4 the group consisting of alkyl substituted-and unsubstituted -phenyl, naphthyl and diphenyl radicals, and wherein the sulfur of the SH group is linked to a nuclear carbon atom of said aromatic radical R, the sulfur present in saidv compound being only in the form of R-SHQ 2. The method of stabilizing a light petroleum solvent which, when boiling, normally causes substantial discoloration of a copper strip immersed therein for thirty, minutes, which cohsists of admixing with said solvent 8, minor pro- 1 portion, from about 0.001 per cent to less than 0.05' per cent, by weight, suflicient discoloration, of thiophenol. I

. 3. Themethod of stabilizing a light petroleum solvent of initial boiling point not lower than about 200 F. and an endpoint of about 400 F. which, when boiling, normally causes substantial to inhibit said discoloration of a copper strip immersed therein for thirty minutes, which consists of admixing with said solvent a minor proportion, from about 0.001 per centto less than 0.05 per cent, by weight, sufiicient to inhibit said discoloration, of thiophenol. v

4. The method of stabilizing a highly aromatic hydrocarbon. cracked distillate fraction which, when boiling, normally causes substantial discoloration of a copper strip immersed therein for thirty minutes, which consists of admixing withsaid'solvent a minor proportion, from about 0.001 per cent to less than0.05 per cent, by weight, sufiicient to inhibit said discoloration, of thiophenol. Y

. EUGENE T. SCAFE.

' JOHN HERMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Nash et al., Principles of Motor Fuel Preparation and Application, vol. II, 1935, page 153. 

